Discourteously departs city after game (6)
I believe the answer is:
rudely
'discourteously' is the definition.
('rudely' can be a synonym of 'discourteously')
'departs city after game' is the wordplay.
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'city' becomes 'ely' (I've seen this before).
'after' says to put letters next to each other.
'game' becomes 'ru' (rugby union).
'd'+'ely'='dely'
'dely' put after 'ru' is 'RUDELY'.
(Other definitions for rudely that I've seen before include "Discourteously" , "In an impolite manner" , "Coarsely" .)